document.write( "Question 444638: The sum of the digits of a two digit number is 15. If the digits are interchanged, the number is increased by nine. What is the original number? \n" ); document.write( "
Algebra.Com's Answer #306446 by oberobic(2304)\"\" \"About 
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These are fun problems because they force you to reconsider what numbers mean.
\n" ); document.write( "Consider 15. What does it mean?
\n" ); document.write( "Well, the 1 means 1*10.
\n" ); document.write( "And the 5 means 5*1.
\n" ); document.write( "So 15 means 1*10 + 5*1 = 10 + 5 = 15.
\n" ); document.write( "We can extend this notion to any sequence of letters, for example 'xy'.
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\n" ); document.write( "Do NOT get confused with 'xy' meaning x * y.
\n" ); document.write( "Here it would mean 10*x + 1*y.
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\n" ); document.write( "xy = the two-digit number, which
\n" ); document.write( "x + y = 15
\n" ); document.write( "yx = xy + 9
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\n" ); document.write( "Looking back we realize that x and y have to be single digits. And for them to = 15, they're either
\n" ); document.write( "9 + 6
\n" ); document.write( "8 + 7
\n" ); document.write( "7 + 8
\n" ); document.write( "6 + 9
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\n" ); document.write( "When the numbers are reversed, the difference is 9.
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\n" ); document.write( "Take 78, when turned around it is 87, which is 9 more.
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\n" ); document.write( "So xy = 78, which is the original number.
\n" ); document.write( "The sum 7+8 = 15.
\n" ); document.write( "When the order is reversed (i.e., 87) the value is 9 more than before the reversal. \n" ); document.write( "
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